1. Technical Field
The present invention relates a method for obtaining high resolution images using a magnetic resonance imaging (MRI) device. More particularly, the present invention relates to a method for obtaining high resolution MRI images by using a sparse reconstruction algorithm.
2. Background Art
In MRI, atomic nuclei are located in a strong magnetic field so as to cause a precession of the atomic nuclei. When a high-frequency signal is applied to the atomic nuclei which are magnetized by a magnetic field generated by the precession, the atomic nuclei are excited into a high energy state. In this state, when the high-frequency signal is removed, the atomic nuclei emit high-frequency signals. Then, the magnetic properties of the materials constituting human body are measured from the emitted high-frequency signals, and the materials are reconstructed, thereby making an image.
Particularly, dynamic MRI is a technology for obtaining a moving image by observing and measuring a temporally changing process, such as cerebral blood flow, heart beat, etc.
In general, when data is obtained in a radial shape within k space, the phase encoding gradient is not used, so that the echo time is short, photographing can be performed without being restrained by breathing and blood flow movement, and an aliasing artifact in data downsampled in a radial shape is generated in a line shape, thereby causing relatively less visual confusion.
However, since an output of radial data in k space requires more data than in a Cartesian grid, scan time of the magnetic resonance imaging increases, and a great amount of calculation is required to optimize the size of downsampled data, thereby causing a system overload.
Also, when data is not obtained in a radial or spiral shape but is obtained in the shape of a Cartesian grid, echo time becomes longer due to the use of the phase encoding gradient, so that the data becomes susceptible to movement of a material object. In order to improve time resolution, it is necessary to reduce the echo time by reducing the number of pieces of obtained data. However, in this case also, there is a problem of causing an aliasing artifact in which images are overlapped and displayed according to the Nyquist sampling limit theory.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.